Automatic downgrade to 4 earlier versions

An easy, automated way to downgrade your current Steam version to one of the four available previous versions. This downgrader is fully compatible with all languages and editions (standard, GOTY...)

Introduction

Fallout 4 was stable between 2019 and 2024 without any updates (version v1.10.163), which allowed many mods to be developed for this version.

However, in 2024, with the release of Season 1 of the series, a "next-gen" update was released. While it improved certain aspects (like widescreen support...), it also introduced bugs and, most notably, broke several mods. Shortly after, a "next-gen update 2" was released, which was considered more stable (but still lacked compatibility with many major mods).

Then, in 2025, an Anniversary Update was launched, first in November and then in December...

All of this has made the modding experience quite unstable for those who enjoy customizing their game.

As a result, downgrading has become an important thing for this game.

Key features of this downgrader

This downgrader is called the "Mulderland's Universal Downgrader"

It works exclusively with the latest Steam version (currently v1.11.221) and will be updated quickly if another update comes out.

It can downgrade to 4 earlier versions :

• v1.10.163 (pre-next-gen version) released in 2019, the recommended version for mods
  
• v1.10.984 (next-gen, update 2) released in 2024
  
• v1.11.169 (anniversary, patch 1) released in 2025-11
  
• v1.11.191 (anniversary, patch 2) released in 2025-12

Unlike other downgrader, this one

• works with all editions (base game, GOTY, or any in-between)
  
• works with all game languages
  
• doesn’t require your Steam credentials

How To

Alright. Here are the instructions :

• Go to Mulderland's page : https://www.mulderland.com/games/fallout-4
  
• Click "Download"
  
• Run the executable (no admin privileges required)
  
• If you encounter any problems, check the help page : https://www.mulderland.com/help
  
  
• Now, you should see this screen :
  
  
• Click "Next" and you’ll see this:
  
  
• Browse to find Fallout4.exe, then click "Next" and you’ll see this :
  
  
• Now, you can select the version you wish to downgrade to.
  
• You can also choose to block future game updates from Steam.
  
• Click "Next". The installer will check if your game version is compatible with the downgrader and will also ask you to confirm that the auto-detection worked correctly.
  
• Click "Yes" and wait a moment (it’s quick, but the time may vary depending on the version you're targeting).

At the end of the installation, your Fallout 4 will be successfully reverted to the selected version.

Important for chinese gamers: Apparently, the software has trouble detecting the game’s language if the game is in Chinese. So, if that's the case, make sure to expand the 'Language Detection' section to select Chinese. For other languages, no action is needed.

FAQ

How it works ?

If you’re comfortable reading code, you can check the installer source code here:
https://github.com/Mulderland/MulderLoad/blob/main/games/fallout-4/steam-downgrader.nsi

Basically, it detects DLCs and game languages by looking for distinctive (unique) files.
(No distinctive file exists for Chinese, which is why you have to help the installer in that case.)

Then it downloads Steam depot deltas. The larger the downgrade, the larger the deltas will be. To go back to v1.11.169 it’s about 28 MB, while going back to v1.10.163 is about 10 GB.

How these deltas were made ?

I wrote some powershell scripts to

• download each steam depot
  
• for each depot, compare files between versions
  
• calculate the delta
  
• compress the delta

They are open source here : https://github.com/mulderf0x/fallout-4-downgrader-maker

Why the downgrader only detects 2 DLCs ?

This is normal. The other DLCs haven’t been modified in many years and don’t need to be downgraded, even to go "back to 2019" (v1.10.163). Therefore, the downgrader has nothing to do for them.

What about the HD textures pack ?

Same story. The HD Textures Pack files hasn’t been modified since 2017. So, the downgrader has nothing to do for it. And the downgrade will work whether you have the HD Textures Pack installed or not.

Troubleshoot

The downgrader refuses to run

This might be related to the Mark of the Web or the self-signed certificate.
Visit https://www.mulderland.com/help for more details.

I have a "disk write error" after using "Block future Steam updates"

If you check this checkbox, it will mark the file "appmanifest_377160.acf" as read-only.

This prevents Steam from making changes to your installation (which is what we want), but not in all situations. For example, you may want to:

• Install a DLC that is currently not installed
  
• Change the game language
  
• Return to the current version of the game

To revert the effect of this checkbox :

• Locate the "appmanifest_377160.acf" file.
  
• Right click on the file > properties > uncheck "readonly" > OK.
  
• Finally, click Retry in Steam.

Thanks

Thanks for reading this guide!

If it helped you, please consider leaving a rating! 😊

[B4DJUJU]

Awesome thanks, works like a charm!

[Mulderland]

Sorry guys, it's fixed.

I'm currently working on the servers to avoid this kind of issues soon. I'll also planning automatic mirror/fallback for people having problem reaching Cloudflare servers.

[B4DJUJU]

Same here

[Your + Mom]

I am also getting the 'Download or hash check failed for 377163.7z.001' error.

[lul]

download speed so slow

[Peelyboy]

Appreciated Mulder. Glad I wasn't just insane. All good now. Thanks for everything

[Mulderland]

Hi guys, sorry I had a temporary problem with a download server, it's fixed now.

[ZeFlyingDonut]

Hello,
Having the same issue here,
Download or hash check failed for 377163.7z.001, aborting...

[VoidiumRex]

This comment is awaiting analysis by our automated content check system. It will be temporarily hidden until we verify that it does not contain harmful content (e.g. links to websites that attempt to steal information).

[Peelyboy]

Hi Mulder, I've tried using the downgrader to return to the .163 version after a fresh install, but every time it runs, it gets stuck on 377163.7z.001, saying "Download or hash check failed for 377163.7z.001, aborting..."

Any ideas? Thanks